Use of human primary cells (from health donors or patients) as physiology- or disease-relevant models provides significant advantages in basic research and therapeutic development for understanding and treating various human diseases, including cancer, cardiovascular and inflammatory diseases. Unfortunately, utility of precious primary cells is largely hindered by lack of effective means for transfection with minimal side effects, particularly in high-throughput mode. Our proposal is specifically designed to address this critical unmet need. Our Phase I studies have demonstrated that our technology is superior than existing methods in transfecting primary cells, especially fully differentiated primary cell monolayers. Phase II work is proposed to develop a 96-well high-throughput transfection system, and to further validate its applicability in extended primary cultures, including both adherent and suspension cells. Success in this project would have notable impact on basic research and therapeutic development by expanding the utility of primary cells, which are the best in vitro models to human. Success in this project will benefit public health by advancing basic research in decoding the functional roles of ~25,000 human genes, and by impacting therapeutic development for fighting diseases like cancer and inflammation.